This study leads ultimately to the preservation of organs by freezing. It is divided into two general portions, basic studies of the mechanism of freezing and the application of new and existing knowledge to the prevention of injury. The basic studies will be directed at the question, how does osmotic dehydration alter membrane permeability? Known situations where permeability is reversibly altered will be studied to determine both the mechanism and how irreversible changes can artificially be made reversible. These studies will utilize human red cells and platelets, mouse myocardial cells, Chinese hamster cells and frog muscle. Research methods will emphasize membrane studies using microelectrode and micropipette procedures, effects of pressure, loss of lipid and protein during hypertonic stress and repair or replacement of their loss, alteration of membrane permeability with chemical agents and study of the effect of stabilizing agents on resistance to osmotic stress. Studies of the prevention of freezing injury will center on means of utilizing the reversible leak of solute across the cell membrane to reduce the amount of penetrating cryoprotectant required, means of increasing cell resistance to osmotic stress and a search for new cryoprotectants. When promising procedures are demonstrated on single cells and tissues, they will be tested on rat and rabbit hearts under perfusion.